子查询返回多于1行-yii2

Question

我的代码，哪里出问题了？

public function actionInsert() {

    $single_date_at  =(new Query())
        ->select('date_at')
        ->from('single_events');

    $single_event_id  =(new Query())
        ->select('id')
        ->from('single_events');

    $user_date_at  =(new Query())
        ->select('birthday')
        ->from('user');

    $user_event_id  =(new Query())
        ->select('id')
        ->from('user');

    $holiday_date_at  =(new Query())
        ->select(['concat(month, - day)'])
        ->from('holiday');

    $holiday_event_id  =(new Query())
        ->select('id')
        ->from('holiday');

    //$date = strtotime($date_at);
    //$formatForView = date("yyyy-mm-dd", $date);

    if(!empty($single_date_at and $single_event_id)) {

        (new Query())->createCommand()->insert('notifications_events',
            [
                'date_at' => $single_date_at,
                'event_id' => $single_event_id,
                'type' => 'single_event',
                'message' => '',
            ])
            ->execute();
    }

    if(!empty($user_date_at and $user_event_id)) {

        (new Query())->createCommand()->insert('notifications_events',
            [
                'date_at' => $user_date_at,
                'event_id' => $user_event_id,
                'type' => 'birthday',
                'message' => '',
            ])
            ->execute();
    }

    if(!empty($holiday_date_at and $holiday_event_id)) {

        (new Query())->createCommand()->insert('notifications_events',
            [
                'date_at' => $holiday_date_at,
                'event_id' => $holiday_event_id,
                'type' => 'holiday',
                'message' => '',
            ])
            ->execute();
    }


}

当我运行此代码时，出现错误

  

SQLSTATE [21000]：违反基数：1242子查询返回多于1行   正在执行的SQL是：插入notifications_events（date_at，event_id，type，message）值（{{{ 1}}），（从birthday中选择user），“生日”，“）”

请帮忙，我需要返回多行，limit（1）在那里是无效的决定